Broadband microwave absorption enabled by a novel carbon nanotube gratings/cement composite metastructure

Abstract

Microwave absorption performance is increasingly needed in cement composites, while multiband or broadband absorption properties are challenging to realize. This study provides a simple and reproducible metastructure for cement composites based on carbon nanotube periodic gratings, exhibiting averaged −15.5 dB reflectivity and 14.2 GHz effective bandwidth in 1–18 GHz. Theoretical requirements for the perfect absorption are analyzed, and the absorption performance and mechanism of the metastructure are studied. Furthermore, three factors affecting absorption performance are investigated, including the gratings periodicity, filling fraction, and the thickness of the cement dielectric. The metastructure with 24 mm periodicity gratings demonstrates multiband absorption performance, showing five peaks lower than −20 dB. The metastructure with 14/24 filling fraction gratings exhibits the reflectivity peak of −38.7 dB and bandwidth for −15 dB of 13.0 GHz, demonstrating broadband nearly perfect absorption performance. In addition, the metastructure with a thinner cement dielectric layer performs better absorbing properties. This study not only proposes an effective method for cement composites to achieve broadband absorption, but also provides cement composites and fireproof materials as novel candidates for the dielectric of metamaterial absorbers, which promotes the application of microwave absorbers to practical construction engineering.